Control of refrigeration



May 23, 1944. A. a. NEWTON CONTROL OF REFRIGERATION Filed D90; 23, 19402 Sheets-Sheet 1 INVENTQR Alwim B. New-tom BY AngRNEv May 23,; 1944. NEN 2,349,671

CONTROL OF REFRIGERATION Filed Dec. 23, 1940 2 Sheets-Sheet 2 INVENTOR.Alwin. B. Nzwloru ATTORN EY Patented May 23, 1944 CONTROL OFREFRIGERATION Alwin B. Newton, Minneapolis, Minn, assignor toMinneapolis-Honeywell Regulator Company, Minneapolis, Minn, acorporation of Delaware Application December 23, 1940, Serial No.371,352

17 Claims.

My invention relates to control of cooling syste s for refrigeratedspaces or compartments wherein it is desirable that the temperature inthe compartment be maintained at a desired value and also that thecooling unit be kept free from frost. My invention is particularlyadaptable to systems employing brine as a cooling agent.

An object of my invention is to provide an improved control arrangementfor cooling systems employin a cooling agent such as brine whereincirculation of the cooling agent is begun only when the cooling unit hasdefrosted and the temperature of the refrigerated space has risen to apredetermined value.

Another object of the invention is to provide an arrangement as setforth in the foregoing object wherein circulation of the cooling agentis prevented when its temperature is above a predetermined value.

Another object of my invention is to provide an improved controlarrangement for refrigerated compartments wherein the flow of coolingagent is modulatingly controlled, but wherein cooling agent ma besupplied only after the cooling unit has defrosted and wherein thesupply is terminated when the temperature of the unit has fallen to apredetermined relatively low value.

Another object is to provide a brine cooling system having a fan forblowing air over the cooling unit and controls for the fan whereby it isoperated whenever there is a demand for refrigeration even thoughrefrigeration is not begun until the unit has defrosted.

Other objects and advantages of m invention will become apparent fromthe following detailed description and annexed drawings wherein:

Figure 1 represents diagrammatically a brine cooling system embodyingone form of my invention therein.

Figure 2 represents diagrammatically a brine cooling system embodying asecond form of my invention.

In Figure l of the drawings I have represented a brine cooling systemfor a compartment H! to be refrigerated. Within the compartment it is acoil II for the cold brine. Numeral l2 desighates a drip pan underneaththe coil for catching water which drips from the coil when it isdefrosted. Numeral i 3 des gnates a fan for blowing air over the coil,the fan being driven by an electric motor is. A source of cold brine isprovided, the brine being cooled within a tank 14. The brine iswithdrawn from the tank H! by a centrifugal circulating pump l5 througha pipe l6 and discharged from the circulator I5 through a pipe I! to thecoolin coil H. The brine is returned from the cooling coil H to the tankM through a pipe I8. The circulator I5 is driven by an electric motor 20by means of a shaft 2|, and the manner of control of the electric motor29 forms the principal feature of my invention.

Means are provided for cooling the brine in the tank 14 including arefrigeration system of the compression type, generally designated bythe numeral 25. The refrigeration system 25 includes a compressor 26driven by an electric motor 271 through a belt 28. The compressordischarges into a condenser 29 through a pipe 36, and the condenser 2i]is connected to an expansion valve 3| by a pipe 32. The outlet of theexpansion valve 3| is connected to an evaporator 33 which is disposed inthe brine in the tank It, and the outlet of the evaporator 33 isconnected to the suction side of the compressor by a pipe 35. Theexpansion valve 3| is of a well-known type having a pressure chambertherein which is connected to a thermal bulb 35 b means of a capillarytube 35. The thermal bulb 35 contains a volatile liquid and is disposedadjacent the outlet of the evaporator 33, and may be clamped thereto asshown so as to be responsive to the temperature of the refrigerant inthe outlet. Valve 3| is of a type which maintains a constant degree ofsuperheat at the outlet of the evaporator.

The compressor motor 21 is controlled by a switch 39. The switch isautomatically operated in response to a temperature bulb 40 which isdisposed in the brine within tank M and which is connected to the switchmechanism by capillary tube ll. The switch 39 is of a known type whichis closed whenever the temperature of the brine in tank l4 rises to apredetermined temperature at which a certain pressure is developedwithin the bulb 45. The switch 39 is opened in response to the bulb 4!]when the temperature of the brine in tank I4 falls to a predeterminedlow value. Whenever the switch 39 is closed, the compressor motor 27 isenergized through the following circuit: From Wire 42 through switch 39,wire 43, the compressor motor 27 and back to wire 44, the wires 42 and44 being connected to any suitable source of power not shown.

The motor 29 which drives the circulator i5 is controlled by a unitarycontrol device 50. The unitary controller 56 comprises a casing withinwhich is mounted an expansible and contractible bellows 5| and a secondexpansible and contractible bellows 52. The bellows 5| is connected to athermal bulb 53 containing a volatile liquid disposed adjacent theoutlet of the brine coil II, by means of a capillary tube 54. Thepressure developed within the bellows 5| is therefore proportional tothe temperature at the outlet of the brine coil II. The bellows 5| hasan operating stem which bears against a pivoted lever 55 which lever isnormally biased in a counter-clockwise direction by a coil spring 56attached to a side wall of the casing of the controller 58. The lever 55carries an insulating pad 51 and attached thereto is a contact bracket58 carrying electrical contacts 59 and 60. The contact 59 cooperateswith a contact 6| carried on a contact bracket 62. The contact 68 liesunderneath or below bracket 62 out of its path of movement andcooperates with a contact 63 carried on a contact bracket 64 secured at64A. The contact brackets 62 and 64 are flexible and bracket 62 bearsagainst a cam 65 which acts as a stop, and the bracket 64 bears againsta cam 66 which acts as a stop. The cams 65 and 66 are mounted onseparate shafts which are adjustable from outside the casing ofcontroller 58 and by adjusting these cams the brackets 62 and 64 aremovable and consequently the position of contacts 6| and 63 is therebyadjustable. When the temperature at the outlet of the coil II rises, thepressure within the bulb 53 and bellows 5| increases causing the bellows5| to expand moving the lever 55 to the right and moving contacts 59 and68 towards their associated contacts 6| and 63. As the temperature atthe outlet of the coil H rises, contacts 59 and 6| are first broughtinto engagement and contacts 68 and 63 are later brought into engagementat a predetermined higher temperature, and normally the bracket 64 is soadjusted that this temperature will be one above freezing such as 33 or34 F., for example. As the temperature at the outlet of the coil |Ifalls, the pressure within bulb 53 and bellows 5| decreases causing thebellows to contract moving lever 55 to the left. This moves contacts 59and 68 away from their associated contacts. Contacts 68 and 63 disengagefirst and contacts 59 and 6| disengage later at a lower temperature, andthis temperature is determined by the adjustment of cam 65 and normallythe adjustment of this cam is such that the temperature at whichcontacts 59 and 6| disengage is relatively low for example, thistemperature may be 18 F.

The bellows 52 is connected to a thermal bulb 18 containing a volatileliquid, and disposed in 4 the brine in tank I4, by means of a capillarytube II. The bellows 52 therefore expands and contracts in accordancewith the temperature afiecting bulb I8. The bellows 52 has an operatingstem which normally bears against a pivoted lever 72 which i normallybiased in a clockwise direction by a coil spring 13 which is attached toa side wall of the casing of the controller 58. At its lower end, lever72 carries a horizontal pusher member 74 which cooperates with a contactbracket I5 and further having an offset extension 15A which cooperateswith the lower end of contact bracket 64. The bracket I5 carries anelectrical contact I6 which cooperates with a contact TI on a terminal18. The lower end of bracket 64 carries a contact 79 which cooperateswith a contact terminal 86. The contacts just described are normallyclosed and are only opened when the temperature of the brine in take l4rises to a rela iv ly high value at which the brine would not produceproper refrigeration in the compartment I8. Thus the automatic switch 39previously described which controls the compressor motor 21 may be setto maintain the brine in tank I4 at a temperature anywhere from 0 F. to15 F., for example. Then the coil spring I3 may be adjusted so that thebellows 52 will open its associated contacts at a temperature somewhatabove 15 F., that is, the bellows 52 may open its associated contactswhen the brine temperature rises somewhat above the value at which it isnormally maintained and which may occur under heavy load requirements.Thus as the temperature eifecting bulb I8 rises, the bellows 52 expands,moving lever I2 to the right. When this happens, the extension 14A ofpusher I4 first engages the bracket 64 moving the said bracket to theright and. disengaging contacts I9 and 80. The parts-may be so adjustedand arranged that this occurs at a temperature of 25 F., for example. Asthe temperature effecting bulb I8 continues to rise, pusher 14 engagesthe lower end of bracket I5 moving contact I6 out oj-f-engagement withcontact TI, and this m a .yi"|: ccur at a temperature of 30 F. of thebri ne, for example.

The controller 59 also includes a relay or starter designated by thenumeral 83, the relay 83 including a winding 84 having an armatureassociated therewith which is arranged to actuate a pair of bridgingmembers 85 and 86. The bridging member 85 carries contacts 81 and 88which are moved into engagement with fixed contacts 89 and 98respectively when the relay coil 84 is energized. Similarly, thebridging member 86 carries contacts 9| and 92 which are brought intoengagement with fixed contacts 93 and 94 when the relay coil 84 isenergized.

Numeral 96 designates an overload device including overload contacts 91which are normally closed, but which are arranged to be opened inresponse to heat from a heating device 98 which is connected in the loadcircuit of motor 28 as will presently be described. The overload device98 is of a known type and therefore need not be described in furtherdetail.

Within the refrigerated compartment I0 is a thermostat I88, thethermostat I88 comprising an expansible and contractible bellows I8Icontaining a volatile liquid which expands and contracts in accordancewith the temperature in the refrigerated compartment I8. The bellows I8| has an operating stem which bears against a lever I82 which ispivoted as shown and which is normally biased in a clockwise directionby a coil spring I83. The lever I82 carries a mercury switch I84 whichhas a pair of electrodes at its left end as shown. Whenever thetemperature within the compartment I8 is below a predetermined value,the thermostat I08 assumes a posithe switch 39 will cycle the compressormotor 21 on and off in response to the bulb 48 so as to maintain thebrine within tank I4 at a predetermined temperature which may be 15 F.,for Inasmuch as the brine is not being example.

circulated through the coil I I at this time, the temperature of coil IIwill rise, and as it rises the pressure developed within bulb 53 willincrease as described above, causing the bellows 5| to expand. As thebellows 5| expands, the lever 55 will be moved to the right firstbringing contacts 59 and BI into engagement as described above. Nothingwill happen when contacts 59 and GI are brought into engagement. As thetemperature at the outlet of coil II continues to increase causingbellows 5| to expand further, the contacts 60 and 63 will be broughtinto engagement. This will occur when the temperature at the outlet ofcoil II has increased to 33 or 34 F. for example, as described above.Inasmuch as this temperature is above freezing, it will not occur untilthe coil II has defrosted. After the contacts operated by bellows 5|have been closed as just described, if the switch I04 is closed orwhenever thereafter that the switch I04 does become closed in a responseto demand, for refrigeration in the compartment I0, a circuit for therelay or starter 83 will be completed as follows: From wire II toterminal I8, through contacts 11 and I6, bracket I5, wire I08, mercuryswitch I04, wire I23, wire I09, bracket 82, contacts BI and 59, bracket58, contacts 60 and 63, bracket 64, contacts I9 and 80, wire IIO,contact 90, wire I I I, contacts 91 of the overload device, wire II2,relay winding 84, wire II3, through terminals H4 and H5 and back to wireH6. The wires I01 and H6 may be connected to any suitable source ofpower not shown. Completion of the circuit just described will energizethe relay 83 causing the bridge members 85 and 86-to move theirassociated contacts into engagement with their respective fixedcontacts. Engagement of contacts 81 and 89 and contacts 88 and 90 willcomplete a maintaining circuit for the winding 84 which is independentof contacts 80 and 83 operated by bellows 5| and contacts I9 and 80operated by bellows 52. This circuit is as follows: From wire I0I toterminal I8, through contacts I1 and I6, bracket I5, wire I08, mercuryswitch I04, wire I23, wire I09, bracket 62. contacts 5! and 59, bracket58, wire III, contacts 89 and 81. bridge member 85, contacts 88 and 98,wire III, contacts 91, wire I I2, winding 84, wire II3, terminals I I4and I I5 back to wire I I6. Thus after completion of this maintainingcircuit, it will be seen that the relay will remain energized eventhough the contacts 68 and 83 should become engaged or even if thecontacts I9 and 80 should become disengaged.

Whenever thermostat I00 closes switch I04 in response to a demand forcooling, the fan motor I9 is energized through the following circuit:From wire I01 to terminal I8, through contacts I1 and I8, bracket I5,wire I08, switch I04, wire I23, wire I24, fan motor I9 and wire I backto wire H6. The fan will be operated Whenever there is a demand forrefrigeration by thermostat I00 even though contacts 60 and 63 have notclosed and this operation of the fan will hasten defrosting of unit IIand closure of contacts 60 and 53.

When contacts 9| and 93 and contacts 92 and 94 are brought intoengagement, a circuit for the circulator motor 20 is completed asfollows: From wire IIJI to terminal I8 through wire I20, heating element98 of the overload device, contacts 93 and 9|, bridge member 89,contacts 92 and 94, wire I2I, motor 20, wire I22 terminals I I4 and H5back to wire I I6. Upon energization of motor 20, the circulator will bestarted in operation and brine will be circulated through the coil I Ifor producing refrigeration in the compartment I0 until the circulatoris stopped. It is to be seen that the circulator is only started whenthe temperature of the coil II has risen to a value at which it hasdefrosted, and when the thermostat I00 indicates a need forrefrigeration in the compartment III. The temperature of the brine intank I4 must also be at a low enough value so that proper refrigerationcan be produced in compartment III, that is, the contacts operated bybellows 52 must be closed.

The motor 20 will remain in operation for circulating brine until thethermostat I00 becomes satisfied so as to open the above describedmaintaining circuit or until the temperature at the outlet of coil I Ifalls to a predetermined low value which may be 18 F, for example, aspointed out above, at which the contacts 59 and SI are disengaged. Thecirculator motor 20 may also be stopped in the event that by reason ofheavy load conditions, the temperature of the brine should rise to ahigh enough value to cause disengagement of contacts I6 and II which arein the above described maintaining circuit for relay 83.

In the event there is an overload in the circuit of the circulator motor20, the heating element 93 will act to cause opening of the overloadcontacts 97 which will deenergize the relay 83 and interrupt the circuitof motor 20.

From the foregoing, it is to be understood that I have provided anarrangement for a brine cooling system wherein circulation of brine isbegun only after the temperature of the cooling unit or coil has risento a value at which the coil has defrosted, and when the thermostat inthe refrigerated compartment indicates a need for refrigeration. Thecirculation of brine continues either until the temperature at theoutlet of the cooling coil falls to a predetermined value or until thethermostat in the refrigerated compartment becomes satisfied. In orderfor the brine c rculator to be operated the temperature of the brine atthe source, that is in the tank I4, must be at a low enough value suchthat proper refrigeration can be produced in the compartment I0. Thoseskilled in the art will appreciate that my arrangement provides foroperating the brine circulator only when refrigeration s required, andonly after the cooling unit has defrosted whereby needless accumulationof frost on the coil is eliminated and there is no necessary operationof the brine circulator.

Referring to the contacts operated by the bellows 52. it is to beunderstood that these contacts need not necessarily be within and a partof the controller 59. but if desired, these contacts may form part of athermostat disposed in or adjacent the tank I 4.

Referring to Figure 2 of the drawings I have shown a modified form of myinvention wherein the flow of brine to the cooling coil is modulatinglyvaried. In Figure 2, numeral 2) indicates a refrigerated compartmenthaving a brine cooling coil 2II therein. Numeral 2I2 designates a pipeconnected to a source of refrigerated brine which may have a temperatureof 15 F. for example, and numeral 2I3 designates a pipe through whichbrine is returned to the source. The inlet of the coil 2II is connectedto the pipe 2!?! the outlet of the coil 2II is connected to the pipe2I3. Various other coils similar o the coil 2 ma l b connected to thepipes 2I2 and 2I3 in the same manner. The

supply of brine to the coil 2 is controlled by a modulating valve 2I4which is of a known type. The valve 2l4 has an auxiliary switch 2I1actuated by the operating mechanism of the valve which is normallyclosed but which is opened when the valve is in closed position. Powerfor operation of the valve 2| 4 is supplied by wires 2I5 and H6 whichare connected to any suitable source of power not shown.

The controls for the valve 2|4 include a thermostat 220 within therefrigerated compartment 2H1. The thermostat 220 is of the proportioningtype including a coiled bimetal element 22l arranged to operate a slider222 which cooperates with an electrical resistance 223. The arrangementis such that the slider 222 slides over the resistance 223 so that theslider and resistance form a potentiometer, the slider moving to theright on a fall in temperature and to the left on a rise in temperature.Numeral 224 designates a second resistance over which the slider 222sweeps. The purposes of the resistance 224 will presently be described.Numeral 226 designates a humidistat comprising a humidistatic element221 of a well-known type and which may be of a type using hair as themoisture responsive means. The humidistatic element 221 is connected toa pivoted slider 228 which is normally biased in a clockwise directionby a coil spring 229 and which is adapted to slide over a resistance236, the slider 228 and resistance 230 forming a second. potentiometer.

The controls for the valve 2|4 also include a relay 23l comprising awinding 232 having an armature associated therewith which is arranged tomove a pair of switch blades 233 and 234 to the right into engagementwith fixed electrical contacts 235 and 236 respectively when the relayis energized. When the relay is deenergized, the switch blades are inthe position shown, and in this position the blade 234 engages a fixedcontact 231. The relay 23l is controlled by a thermostatic device 246and a second thermostatic device 24!. The thermostatic device 240comprises an expansible and contractible bellows 242 connected to athermal bulb 243 by capillary tube 244. The bulb 243 contains a volatileliquid and is disposed adjacent the inlet of the coil 2 so as to beresponsive to the temperature thereof, so as to cause the bellows 242 toexpand and contract in accordance with the temperature at the inlet endof coil 2H. The bellows 242 has an operating stem which normally bearsagainst a pivoted lever 245 which is normally biased in a clockwisedirection by a coil spring 246. The lever 245 carries a mercury switch241 having a pair of electrodes at its left end as shown. When thetemperature at the inlet of coil 2 is below a predetermined value thebellows 242 is in a contracted position and has the mercury switch 241pen as shown. Whenever the temperature at the inlet of coil 2 rises to apredetermined value a pressure is developed within the bulb 243 andbellows 242 which causes the bellows to expand sufficiently to movelever 245 in a counterclockwise direction causing the mercury switch 241to close.

The thermostatic device 24l is very similar to the device 242, thedevice 24! comprising an expansible and contractible bellows 250connected to a bulb 25| by a capillary tube 252. The bulb 25| contains avolatile liquid and is disposed adjacent the outlet of the coil 2 so asto be responsive to the temperature thereof and to thereby cause thebellows 250 to expand and contract in accordance with the temperature atthe outlet of the coil. The bellows 250 has an operating' system whichnormally bears against a pivoted lever 253 which is normally biased in aclockwise direction by a coil spring 254. The lever 253 carries amercury switch 255 which is adapted to be closed when the temperatureeffecting bulb 25l is above a predetermined value. Whenever thetemperature affecting bulb 251 falls below this predetermined value, thebellows 250 contracts moving lever 253 in a clockwise direction so as tocause mercury switch 255 to open.

The thermostatic device 240 is normally set so that mercury switch 241is not closed until the temperature affecting bulb 243 has risen to avalue of 33 or 34 F. for example, that is, at a temperature high enoughto insure that the coil 2| I has defrosted. The thermostatic device 2 isset so that the mercury switch 255 is normally closed except when the.temperature affecting bulb 25l falls to a predetermined relatively lowvalue which may be 18 F. for example. This temperature of 18 F. is verylittle above the temperature of the brine being admitted to coil 2| I,the temperature of which may be 15 F. as mentioned above, and indicatesthat coil 2 II has accumulated a substantial amount of frost and isdoing very little cooling. Switch 255 acts as a defrosting switch aswill presently be described.

The left end of resistance 223 is connected to the valve operatingmechanism of valve 2I4 by wires 260 and 26l as shown. The right end ofresistance 223 is connected to the operating mechanism of valve 2 l4 bywires 262 and 263 as shown. The midpoint of resistance 224 is connectedto the fixed contact 236 by wires 264 and 265. The switch blade 234 ofrelay 23l is connected to the operating mechanism of valve 2| 4 by awire 266 as shown. The lower end of resistance 230 is connected to wire26l by a wire 216 and the upper end of resistance 230 is connected towire 263 by wires 212 and 213. Slider 228 is connected to the junctureof wires 264 and 265 by a wire 215. The contact 231 with which blade 234of relay 23| is in engagement when the relay is deenergized is connectedto the juncture of wires 212 and 213 by wire 214 as shown. From theforegoing, it is obvious that the potentiometers formed by thetemperature responsive controller and the humidity responsive controllerare connected in parallel. The temperature responsive controller 220forms the primary control for the valve 214 and the humidity controlleracts as a compensator. The control arrangement as described for thevalve 2 l 4 is substantially the same as that disclosed in detail in thepatent of John E. Haines No. 2,173,331 and reference may be had to thispatent for a detailed disclosure of the structure and operation ofystems of this type.

The operating mechanism of the valve 2l4 is such that when the voltagedrop between wires 26! and 266 i reduced relative to the voltage dropbetween wires 263 and 266 the valve is moved in opening direction andwhen the voltage drop between wires 263 and 266 is reduced relative tothe voltage drop between wires 26] and 266, the valve is moved inclosing direction. The potentiometers formed by controllers 220 and 226control the relative amounts of the voltage drops just referred to andthereby the position of valve 2i 4 is controlled in the same manner asin the Haines patent referred to above. When relay 23l is deenergized asshown in Figure 2, the sliders 222 and 228 are disconnected from theoperating mechanism of the valve 2l4 inasmuch as blade 234 is out ofengagement with contact 236 and, as

a result, the controllers 226 and 226 are ineffective to exert anycontrol over the valve 214. With the relay deenergized as shown, blade234 is in engagement with contact 231, and under these circumstanceswires 263 and 266 are directly connected so that there is no voltagedrop between them and, as a result, the valve 214 i operated to fullyclosed position. This circuit for causing complete closure of the valveis as follows: From valve 2H5 through wire 266 to switch blade 23 5,contact 231, wire 214 and wire 213 back to wire 263 which is connectedto valve 2 I l.

The controller 228 may have a total differential of 5 for example. Thatis, the slider 222 may be at the left end of resistance 223 when thetemperature in the refrigerated space is 35 F. and the slider may be atthe right end of resistance 223 when the temperature in the refrigeratedspace 2E8 is 30. When the temperature in the refrigerated space 2l8 isat the desired value, however, the slider 222 assumes a positionsubstantially at the midpoint of resistance 223 and under thesecircumstances the temperature is 33 F. The operating differential of thecontroller 228 is relatively narrow however, and movement of the slider222 over the resistance 223 an amount corresponding to a temperaturechange of only one or two degrees in the refrigerated compartment issufficient to cause the valve 2M to operate entirely between its fullyopened and closed positions. As in the Haines patent, the controller 226which acts as a compensator has less effect on the operating mechanismof the valve 214 than does the controller 22!]. The function of thecontroller 226 is to move the control point of the controller 226 fromone position to another along the resistance 223. The manner ofoperation of the valve 2M in response to the controllers 22:") and 226will be explained more in detail presently.

With the parts in the position shown, the valve 2M is closed, and withno brine flowing through the coil 2 its temperature rises and when itstemperature has risen to a value of 33 or 34 F. at which the coil hasdefrosted, the bulb 223 will cause the bellows 242 to expandsufliciently to close mercury switch 261. When mercury switch 241 closesa circuit is completed for the winding 232 of relay 23l as follows: Froma wire 28!] through winding 232, wire 28f, mercury switch 241, wire 262to wire 283, the wires 286 and 283 being connected to any suitablesource of power not shown. At the time relay 23l is energized, themercury switch 255 will be closed because, as pointed out above, thisswitch is normally closed unless the temperature at the outlet of coil 2falls to a predetermined low value of 18 F. for example. When relay 23!is energized, blades 233 and 234 are moved to the right into engagementwith their associated contacts 235 and 236, blade 234 moving out ofengagement with contact 231 and interrupting the above described closingcircuit for valve 2 l 4. Engagement of blade 234 with contact 236completes the cir-- cuit connection from the slider 222 of thermostaticcontroller 220 through resistance 224 to wire 266, that is, to theintermediate wire connected to the operating mechanism of valve 2H1.Engagement of blade 234 with contact 236 also connects slider 228 withthe intermediate wire 266 of valve 2M inasmuch as slider 228 isconnected to wire 265 by wire 215. Completion of these connectionsplaces the thermostatic controller 220 in operative control of the valve2M with the humidity responsive controller 226 now efiective to act as acompensator.

At the time the relay 23I is energized, the controller 220 will usuallyhave slider 222 at the left end of resistance 223, it being understoodof course that at this time the temperature in the refrigeratedcompartment will be relatively high inasmuch as the temperature at theoutlet of coil 2 has risen to 33 or 34 F. for causing closure of mercuryswitch 241. When the controllers 228 and 226 are in operative control ofthe valve 2M, they control the relative voltage drops between wires 26!and 266 and between wires 263 and 266. Thus at the time that relay 231is energized with the slider 222 of controller 220 at the left end ofresistance 223, the voltage drop between wires 26l and 266 will be at aminimum relative to the voltage drop between wires 263 and 266. Underthese circumstances the valve 214 will be operated to wide open positionto admit a maximum flow of brine to the coil 2! I.

When valve 2M is moved out of closed position, auxiliary switch 2 l 1 isclosed completing a maintaining circuit for relay 23I as follows: Fromwire 238 through winding 232, wire 284, auxiliary switch 2H, wire 2B1,contact 235, blade 233, wire 285, mercury switch 255, wire 286 to wire263. This circuit is independent of switch 241.

As the temperature in the refrigerated compartment falls due to the flowof brine through the coil 2| l, element 22! will cause slider 222 tomove to the right along resistant'e 223. As slider 222 approaches themidpoint of resistance 223 the controller 220 will begin to effectivelycontrol the valve 2 l 4 and will move it towards closed position, thevalve assuming a position of course depending upon the position of theslider 222 with respect to the resistance 223. Whenever the slider 222is moved out of its midposition with respect to resistance 223, thevalve 2I4 will be moved correspondingly to adjust the flow of brine soas to maintain the desired temperature in the refrigerated compartment2H! which, for example, may be 33 F. as described above. Thus if thetemperature rises above the desired value of 33, the slider 222 will bemoved to the left along resistance 223 which will reduce the Voltagedrop between wires 268 and 264 relative to the voltage drop betweenwires 262 and 264. Inasmuch as wires 260 and 262 are connected to wires26l and 263 respectively and as wire 264 is connected to wire 266through the switch blade 234, the variations in the voltage drops willbe impressed on the operating mechanism of valve 2M and it will be movedin opening direction an amount sulficient to cause the temperature toreturn to the desired value of 33 F. causing the slider 222 to be movedback to the midpoint of resistance 223. In the event the temperature inthe refrigerated compartment falls below the desired value of 33 F., theslider 222 will be moved to the right along resistance 223 and thevoltage drops will be varied relatively in the opposite direction, andvalve 2! will correspondingly be moved an amount in closing directionproportional to the amount that the temperature deviates from thedesired value of 33 F. This movement of the valve in closing directionwill cause the temperature to return towards normal and the slider 222will be returned to its position at the midpoint of resistance 223.

As pointed out above, the controller 226 is a compensating controllerand it has a smaller effect upon the operating mechanism of the valve2|4 than the controller 226. The efiect of the compensating controller226 is to move the con trol point of controller 220 from one position toanother along resistance 223. Thus upon an increase in humidity in therefrigerated compartment indicating a need for more dehumidification,the humidity responsive element 221 will expand causing the slider 228to move downwardly along resistance 230. Inasmuch as the controllers 226and 226 are connected in parallel, this action of controller 226 has thesame effect as movement of slider 222 to the left along resistance 223.In other words, the voltage drop between wires 26| and 266 will now bereduced relatively to the voltage drops between wires 263 and 266, andthe valve will tend to move in opening direction an amount proportionalto the variation in humidity. As a result of this movement of the valve2|4 in opening direction, the controller 226 will now have to respond toa lower temperature in the refrigerated compartment 2 0, that is, itwill have to move to the right along resistance 223 in order to assume aposition wherein it may now again effectively assume control of thevalve 2 l4. In other words, movement of the valve 2 l4 in response tothe controller 226 causes the controller 220 to assume a new controlpoint at which it controls the valve 2|4. Upon a decrease in humidity inthe refrigerated compartment slider 228 is moved upwardly alongresistance 230 and the voltage drops between wires 26| and 266 andbetween wires 263 and 266 are varied relatively in the opposite manner.As a result, the valve 2 I4 is moved in a closing direction and thecontrol point of controller 226 is moved to the left proportionately acorresponding amount.

Thus as described above, the controllers 220 and 226 jointly control theadmission of refrigerant, that is, brine to the cooling coil 2|| so asto maintain both the temperature and humidity at the proper values. Thecontrollers 220 and 226 may be so correlated as to maintain a desiredeffective temperature in the compartment 2| 0.

Resistance 224 is known as a corrector resistance, the purpose of whichwill now be explained. When the slider .222 of controller 220 moves inone direction or the other along resistance 223, the relative voltagedrops between wires 26| and 266 and between wires 263 and 266 is varied,as pointed out above. However, as the slider 222 approaches one end orthe other of the resistance 223 the rate of variation in these relativevalues of voltage drops changes, that is, it is not uniform, and tocompensate for this lack of uniformity in the rate of change of thevoltage drops, the resistance 224 is employed. As the slider 222 movesto the right or left, more or less of resistance 224 is placed incircuit with wires 264 and 265, that is the intermediate wire leading tothe operating mechanism of valve 2 I4. This ad. ditional resistanceplaced in circuit with the intermediate wire of the operating mechanismof the valve compensates for the lack of uniformity in the rate ofvariation in the voltage drops. This is explained more particularly inthe patent to Haines referred to above.

As the flow of brine through the cooling coil 2H progresses, the coolingload in the refrigerated compartment will be reduced and correspondinglya reduced flow .of brine will be required to maintain the desiredtemperature of 33 F. Normally there will be a rise in temperature of thebrine as it passes through the coil 2| For instance, if it is admittedat a temperature of 15 F., normally the temperature at the outlet of thecoil will be in the vicinity of 25 F. As the flow of brine through thecoil is reduced in volume, normally the temperature at the outlet of thecoil will tend to rise somewhat due to the reduced flow so that mercuryswitch 255 will remain closed. However, if frost accumulates on the coil2| to such an extent as to materially impair its refrigerativeeiiiciency, the brine passing therethrough will not absorb very muchheat and consequently the temperature of the brine at the outlet willfall to a lower value and may fall to a temperature below 18 F., causingthe pressure within bulb 25| and bellows 250 to {diminish contractingbellows 250 and opening switch 255. Opening of this switch interruptsthe maintaining circuit of relay 23|, deenergizing the relay causing theswitch blades 233 and 234 to assume the positions shown in Figure 2.This disconnects the controllers 220 and 226 from the valve 2|4 andagain completes the circuit above described for causing complete closureof valve 2|4. Switch 241 will of course be open at the time switch 255is opened because switch 241 is closed only when the temperature at theinlet of coil 2 has risen to 33 F. or 34 F. and this switch has arelatively narrow differential. That is, the temperature at the inlet ofthe coil would not be as high as 33 F. or 34 F. when it is 18 F. at theoutlet. When the relay is deenergized in response to opening of switch255, it will not be reenergized for causing the valve 2|4 to reopenuntil coil 2 has defrosted so as to close switch The coolingrequirementsin compartment 2|6 may become substantially fully metwithout the coil 2|| having become frosted. The controller 226 mayoperate the valve 2|4 to fully closed position or to substantially fullyclosed position without the coil 2| I having become frosted, that is,the cooling requirements in the compartment 2|0 may become substantiallyfully met so that little or no flow of brine is required to maintain thetemperature at the desired value of 33 F. If the valve 2|4 is closed inthis manner the auxiliary switch 2|'| will be opened, interrupting themaintaining circuit of relay 23| and deenergizing the relay. If therelay is thus deenergized, the controllers 226 and 226 will bedisconnected from the valve 2|4 and the relay 23| will not be againenergized until switch 241 has closed.

Fromthe foregoing it will be apparent to those skilled in the art thatin the present embodiment of my invention I have provided a verydesirable arrangement wherein refrigeration is initiated only after thecooling unit or coil has defrosted,

and during the progress of refrigeration the flow of cooling agent isvaried in a manner to maintain a desired temperature value at all timesin the refrigeration compartment. When the temperature of the brine atthe outlet of the coil falls to a relatively low value indicating thatthere is a substantial accumulation of frost on the coil, the flow ofbrine is discontinued until defrosting of the coil takes place. Also,when the cooling requirements in the refrigerated compartment aresubstantially or fully met the supply of brine or other cooling agent isterminated and it is not reinitiated until the temperature of the unithas risen to a predetermined value.

The embodiments of my invention which I have disclosed arerepresentative of its preferred forms and are illustrative of variousmodifications and changes which may be made in it. There are forms andvariations of the invention which will occur to those skilled in the artwhich have not been disclosed herein. My disclosure is therefore to beinterpreted as illustrative rather than in a limiting sense and theinvention is to be limited only as determined by the claims appendedhereto.

I claim as my invention:

I. In apparatus of the character described, in combination, meansforming a compartment to be refrigerated, a cooling unit in saidcompartment, means forming a source of cold brine, means for controllingthe circulation of brine through said unit, control apparatus associatedwith the controlling means comprising means responsive to thetemperature of the unit and means responsive to a condition of the airin the compartment for initiating circulation of brine When thetemperature of the unit reaches a value high enough to have defrostedthe unit and said condition has attained a predetermined value, andmeans responsive to the temperature of the brine for preventingcirculation of brine when the temperature of the brine is above apredetermined value.

2. In apparatus of the character described, in combination, meansforming a compartment to be refrigerated, a cooling unit in saidcompartment, means forming a source of cold brine, means for controllingthe circulation of brine through said unit, control apparatus associatedwith the controlling means comprising means responsive to thetemperature of the unit and means responsive to a condition of the airin the compartment for initiating circulation of brine when thetemperature of the unit reaches a value high enough to hav e geggsteitlg e unit and said condition has attained a predetermined value,means for cooling said brine, means re sponsive to the temperatureof thebrine controlling the cooling means, and means responsive to thetemperature of the brine for preventing circulation of brine when thetemperature of the brine is above a predetermined value.

3., ,In apparatus of the character described, in combination, meansforming a compartment to be refrigerated, a cooling unit in saidcompartment, means whereby cooled brine may be circulated through theunit, control apparatus for controlling the flow of brine through theunit comprising means responsive to a psychrometric condition of the airin the compartment and means responsive to the temperature of the unit,the control apparatus being arrafi'gd tdinitiate circulation of brineonly when the unit has reached a temperature at which it has defrosted,and means influenced by the temperature of the brine to terminatecirculation thereof through the unit when it is below a predeterminedvalue, said means responsive to a psychrometric condition of the air inthe compartment being of a ype arranged to modulatingly Vary the flow ofbrine after flow has been initiated.

4. In apparatus of the character described, in combination, meansforming a compartment to be refrigerated, a cooling unit in saidcompartment, means whereby cooled brine may be circulated through theunit, control apparatus for controlling the flow of brine through theunit comprising means responsive to a psychrometric condition of the airin the compartment and means responsive to the temperature of the unit,the control apparatus being arranged to initiate circulation of brineonly when the unit has reached a temperature at which it has defrosted,and means influenced by the temperature of the brine to terminatecirculation thereof through the unit when it is below a predeterminedvalue, said control apparatus comprising a valve controlling the brineflow, and means comprising a relay controlling the valve, said meansresponsive to the temperature of the unit controlling an energizingcircuit for the relay and said means influenced by the temperature ofthe brine controlling a maintaining circuit for the relay.

5. In apparatus of the character described, in combination, meansforming a compartment to be refrigerated, a cooling unit in saidcompartment, means whereby cooled brine may be circulated through theunit, control apparatus for controlling the flow of brine through theunit comprising means responsive to a psychrometric condition of the airin the compartment and means responsive to the temperature of the unit,the control apparatus being arranged to initiate circulation of brineonly when the unit has reached a temperature at which it has defrosted,and means influenced by the temperature of the brine to terminatecirculation thereof through the unit when it is below a predeterminedvalue, said means responsive to a psychrometric condition of the air inthe compartment including a valve, and being of a type arranged tomodulatingly vary the flow of brine after flow has been initiated.

6. In apparatus of the character described, in combination, meansforming a compartment to be refrigerated, a cooling unit in saidcompartment, means whereby cooled brine may be circulated through theunit, control apparatus for controlling the flow of brine through theunit comprising means responsive to a psychrometric condition of the airin the compartment and means responsive to the temperature of the unit,the control apparatus being arranged to initiate circulation of brineonly when th unit has reached a temperature at which it has defrosted,means influenced by the temperature of the brine to terminatecirculation thereof through the unit when it is below a predeterminedvalue, said means responsive to a psychrometric condition of the air inthe compartment including a valve,

and being of atype arranged to modulatingly I vary the flow of brineafter flow has been initiated, means comprisin a relay cooperating withsaid valve means and arranged to cause said valve to be controlled bysaid means responsive to a psychrometric condition so as to close saidvalve, circuit means for energizing said relay controlled by said meansresponsive to the temperature of the unit, and means forming amaintaining circuit for the relay controlled by said means influenced bythe temperature of the brine.

7. In apparatus of the character described, in combination, meansforming a compartment to be refrigerated, a cooling unit in saidcompartment, means whereby a cooling agent may be circulated throughsaid unit, valv means controlling the fiow of cooling agent through saidunit, means including a relay controlling the valve means, meansresponsive to a condition of the unit controlling an energizing circuitfor the relay, said relay being arranged to normally cause opening ofthe valve means upon energization thereof, means responsive to acondition of the unit controlling a maintaining circuit for the relay,the relay being arranged to cause closure of the valve means upondeenergization of the relay, and means responsive to a psychrometriccondition of the air in the compartment arranged to modulatingly varythe position of the valve means after the valve means has been opened inresponse to energization of the relay.

8. In apparatus of the character described, in combination, meansforming a compartment to be refrigerated, a cooling unit in saidcompartment, means whereby cooled brine may be circulated through theunit, control apparatus for controlling the flow of brine through theunit comprising means responsive to a psychrometric condition of the airin th compartment and means responsive to the temperature of the unit,the control apparatus being arranged to initiate circulation of brineonly when the unit has reached a temperature at which it has defrosted,said means responsive to a psychrometric condition of the air in thecompartment being of a type arranged to modulatingly vary the flow ofbrine after flow has been initiated.

9. In apparatus of the character described, in combination, meansforming a compartment to be refrigerated, a cooling unit in saidcompartment, means whereby a cooling agent may be circulated through theunit, control apparatus for controlling the flow of cooling agentthrough the unit comprising means responsive to a psychrometriccondition of the air in the compartment and means responsive to thetemperature of the unit, the control apparatus being arranged toinitiate circulation of cooling agent only when the unit has reached atemperature at which it has defrosted, said means responsive to apsychrometric condition of the air in the compartment being of a typearranged to modulatingly vary the flow of cooling agent in accordancewith flow requirements necessary to maintain said condition at apredetermined value, and means associated with said last means fordiscontinuing the flow of cooling agent entirel when flow requirementshave been reduced to a minimum until the unit again reaches saidaforementioned temperature.

10. In apparatus of the character described, in

' combination, means forming a compartment to be refrigerateda coolingunit in said compartment, means forming a source of coolin agent, meansfor controlling a circulation of cooling agent through said unit,control apparatus associated with the controlling means comprising meansresponsive to the temperature of the unit,

means responsive to a condition of the air in the compartment forinitiating circulation of cooling agent when the temperature of the un tmeans comprising a relay controlling the valve, said means responsive tothe temperature of the unit controlling an energizing circuit for therelay and means associated with the valve controlling a maintainingcircuit for the relay, said last means being arranged to interrupt themaintaining circuit when the valve is in a minimum flow position.

12. In apparatus of the character described, in combination, meansforming a compartment to be refrigerated, a cooling unit in saidcompartment, means whereby cooling agent may be circulated through theunit, control apparatus for controlling the flow of cooling agentthrough the unit comprising means responsive to a psychrometriccondition of the air in the compartment, means responsive to thetemperature of the unit,

the control apparatus being arranged to initiate circulation of COOIillgagent only when the unit has reached a temperature at which it hasdefrosted, means influenced by the temperature of the cooling agent toterminate circulation thereof through the unit when it is below apredetermined value, said means responsive to a psychrometric conditionof the air in the compartment including a valve, and being of a typearranged to modulatingly var the flow of coolin agent after flow hasbeen initiated, means comprising a relay cooperating with said valvemeans and arranged to cause said valve to open or close, circuit meansfor energizing said relay controlled by said means responsive to thetemperature of the unit, means forming a, maintaining circuit meansassociated with said valve means for inreaches a value high enough tohave defrosted the unit and said condition has attained a predeterminedvalue, and means for circulating airover said unit whenever said meansresponsive to a condition of the air in the compartment demandscirculation of cooling agent even though the temperature of the unit hasnot risen high enough to defrost it.

11. In apparatus of the character described, in combination, meansforming a compartment to be refrigerated, a cooling unit in saidcompartment, means whereby cooling agent may be circulated through theunit, control apparatus for controlling the flow of cooling agentthrough the unit comprising means responsive to a psychrometriccondition of the air in the compartment and means responsive to thetemperature of the unit, the control apparatus being arranged toinitiate circulation of cooling agent only when the unit has reached atemperature at which it had defrosted, said control apparatus comprisinga valve controlling the flow of cooling agent,

terrupting said maintainin circuit when the valve is in a minimum flowposition.

13. In apparatus of the character described, in combination, meansforming a compartment to be refrigerated, a cooling unit in saidcompartment, means whereby a cooling agent may be circulated through theunit, said agent being of a type which does not change its physicalstate at normal operating temperatures of said unit, means responsive tothe temperature of the unit for initiating flow of cooling agent afterthe unituntil the unit has defrosted.

14. In apparatus" of the character described, means forming acompartment to be refrigerated, a cooling unit in said compartment,means comprising a source of cold brine, means for controlling acirculation of brine through said unit,

; control apparatus associated with the controlling means comprisingmeans responsive to the temperature of the unit, means responsive to acondition of the air in the compartment for initiating circulation ofbrine when the temperature of the unit reaches a value high enough tohave defrosted the unit and said condition has attained a predeterminedvalue, and means for circulating air over said unit whenever said meansresponsive to a condition of the air in the compartment demandscirculation of brine even though the temperature of the unit has notrisen high enough to defrost it.

15. A system of the character described comprising in combination, aspace to be cooled, a

cooling coil for cooling said space, means conducting cooling fluid tosaid coil for circulation therethrough, said fluid being of a type whichdoes not change its physical state under normal operating temperaturesof said coil, and means for defrosting said coil, said defrosting meansincluding means for stopping circulation of fluid through said coil whenthe temperature of the fluid leaving said coil is so low as to indicatea frosted condition of the coil and preventing such circulation untilthe temperature of the fluid has risen to a value indicating that thecoil has been defrosted.

16. A system of the character described comprising in combination, aspace to be cooled, a

cooling coil for cooling said space, means conducting cooling fluid tosaid coil for circulation therethrough, said fluid being of a type whichdoes not change its physical state under normal operating temperaturesof said coil, and means for defrosting said coil, said means includingmeans for stopping circulation of fluid through said coil when thetemperatureof the fluid leaving said coil is so low as to indicate afrosted condition of the coil and preventing such circulation until thetemperature of the fluid has risen to a value indicating that the coilhas been defrosted, and means responsive to a psychrometric condition ofthe air in said space preventing circulation of fluid through said coilupon a decrease in the value of said condition.

17. A system of the character described comprising in combination, aspace to be cooled, a cooling coil for cooling said space, meansconductin coolin fluid to said coil for circulation therethrough, saidfluid being of a type which does not change its physical state undernormal operating temperatures of said coil, and means for defrostingsaid coil, said means including means for stopping circulation of fluidthrough said coil when the temperature of the fluid leaving said coil isso low as to indicate a frosted condition of the coil and preventingsuch circulation until the temperature of the fluid has risen to a valueindicating that the coil has been defrosted, and means responsive to apsychrometric condition of the air in said space preventing circulationof fluid through said coil upon a decrease in the value of saidcondition, said defrosting means acting, each time the circulation offluid is stopped, to prevent further circulation until the temperatureof the fluid is such as to indicate that the coil has been defrosted.

ALWIN B. NEWTON.

